cold start idle issues

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loveN2O

New Member

May 15, 2011

6

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0

May 15, 2011

#1

• May 15, 2011

• #1

i have read through a lot of posts on here and still have yet to track down my problem. cold starts it stays running but very rough for about 3-5 min then it runs fine. 2000 gt all stock except bbk off road x and cat back. brand new IAC installed cant find any vacuum leaks mass air clean good fuel pressure 35 psi new fuel filter new plugs running out of options here!! lol it did just start throwing O2 codes i think my MIL's went bad maybe but where should i go next i have a new ECU coming tomorrow for it. should i get new O2 sensors? i also read the the IAT little sensor could be bad i have not changed it. the car runs just fine at all other time but the first start for the day or if it sits for a few hours and cools completely it chokes and pukes for a couple minutes. please somebody try and help me!! thanks so much!!

 

wmburns

SN Certified Technician

Aug 14, 2009

5,892

514

204

Houston Texas

May 16, 2011

#2

• May 16, 2011

• #2

Why are you replacing the ECU/PCM? Seems silly to spend time diagnosing when there are plans to replace such a major part.

 

fiveoho

15 Year Member

Apr 28, 2005

1,958

16

69

TN

May 17, 2011

#3

• May 17, 2011

• #3

my 2000 does this as well. after the initial 'warm up' , its fine. cold starts it tends to idle very rough, usually until it dies. starts right back up and runs just fine. if i let it run for 10 min prior to driving it, there isnt a problem. i have a suspicion it has something to do with the aftermarket CAI, TB and plenum.

 

trinity_gt

10 Year Member

Jan 31, 2003

3,125

81

99

Canada

May 17, 2011

#4

• May 17, 2011

• #4

You might want to put a fuel pressure gauge on the rail and see what happens to the rail pressure after you shut the car off and let it sit for a while. Perhaps you've got a fuel injector leaking down (bleeding off pressure) and flooding a cylinder.

 

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loveN2O

New Member

May 15, 2011

6

0

0

May 17, 2011

#5

• May 17, 2011

• #5

the intake and all that stuff on this one is all stock but the symptoms match completely. mine normally wont die when it starts to choke and puke but i tried shutting it off and re starting when it does it and it runs perfect then??? WTF is wrong with this thing?? fuel pressure as i stated above is great. my new ecu came today so im installing it in the morning see what happens. normally this problem points to the idle air control like i said IAC so if you have not tried that on yours then most deffinitely put a new one on 50 bucks at advance auto but mine didnt help thats why its throwing me way off. im lost if the new ecu dont help unless perhaps the new iac is bad i have got new parts before that were no good who knows guess i will cross my fingers and see what happens in the morning.

 

fiveoho

15 Year Member

Apr 28, 2005

1,958

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69

TN

May 18, 2011

#6

• May 18, 2011

• #6

havent replaced my IAC so that could very well be it.

good luck with yours

 

DJ Fury

Member

Aug 22, 2009

72

1

9

May 18, 2011

#7

• May 18, 2011

• #7

I had this problem as well. I replaced my IAC with an advance auto part and continued to have issues, though slightly different in behavior. On a suggestion from a friend as well as having easy access, I replaced my IAC again only with a ford motorcraft part (9F715) and everything was as it should be again.

I will admit that the ford part is significantly more expensive but that also got me thinking as to why that is... I will also admit this may have been a fluke bad part I had from advance, and putting a ford part on just got me back to normal, but I swear I've heard this somewhere in my years of reading mustang forums.

If you have the means and you suspect a bad IAC, buy the ford part and avoid phantom troubleshooting like I did.

 

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loveN2O

New Member

May 15, 2011

6

0

0

May 18, 2011

#8

• May 18, 2011

• #8

you know i suspected the same thing with the advance auto part as well i did not get my new ecu in today but i may have time to get it tomorrow so here is what im thinking about doing. going back to advance and asking for an exchange right??? gimme another and i will try it. then i think what i will do is take one off a known running car and try it right. then if that dont work it has to be either a ground issue which i doubt or the ecu. there is nothing else left but thanks for the help and i do agree about the ford part being better

 

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loveN2O

New Member

May 15, 2011

6

0

0

May 20, 2011

#9

• May 20, 2011

• #9

switched IAC again and car still didnt idle right!!!